Full authority digital electronic controls (FADEC's) are being applied to numerous aircraft engines, and it is desirable to apply them to helicopter engines, particularly high performance helicopters. As a necessary safety measure, full mechanical backup is required for such electronic controls. Particularly in the case of helicopters, the transition between electronic control and manual control upon failure of the former can cause a highly undesirable transient in the fuel supply to the engine. The failure or shutdown of the electronic control is itself a sufficiently significant occurrence, such that the introduction of an engine speed change due to a transient in fuel supply occasioned by the transfer is not only highly undesirable but also probably dangerous.
Insofar as applicants are aware, the prior art has approached the problem of transfer from electronic to manual backup control in a helicopter by attempting to reduce the magnitude of the transient so that the change in helicopter performance upon switching from electronic to manual control is not very significant. It would be desirable, of course, to achieve a bumpless transfer, but insofar as applicants are aware, such a transfer has not been available heretofore.